AnalogIn test requires that analog input pins also support digital output function

[maclobdell]

Need an alternative way to test analog pins when they don't support digital output for some rare cases. A resistor ladder is preferred such that a different value can be read on each analog pin. This would confirm that the analog pins are configured correctly for individually measuring on each pin.
Alternatively, have a way to fly-wire the pwm-capable digital signals (selectable) to a capacitor to ground, then to the resistors in parallel to the analog pins.

[BlackstoneEngineering]

I think it is a fair assumption that all pins can be digital IO. This assumption is an underlying assumption made in the mbed SDK, so having a ping that cannot do GPIO would be an SDK implementation error, not a test case?

@sg- care to comment on this one?

[sg-]

My previous though was that a resistor ladder would provide the coverage needed and avoid this case where analog pins are not digital capable

[BlackstoneEngineering]

Will consider changing to resistor ladder for next revision. But how often is it the case that a pin can do analog in but not digital out?

[maclobdell]

I think that most mcus these days probably do offer both analog and digital capabilities on the same pin. But there are definitely potential cases where they do not - most probably on high-precision ADCs. In my opinion, a simple circuit that isolates the feature under test (analogin, not analogin + digitalout) would be preferred.

[BlackstoneEngineering]

I do not disagree, the problem is we're pretty far down the path to getting these produced, making any HW changes would delay the release of the CI Test Shield by 1-2 months. Is this worth it?

Also, wouldnt adding a resistor ladder across A0-5 messup the analogout test? Or are you proposing a resistor ladder across A0-3 with A4-5 being loopback?

[BlackstoneEngineering]

As a solution I have added the 'assumptions' tests, which will check the assumptions made in the tests. In this case the TESTS/assumptions/analogin/analogin.cpp test will check that the AnalogIn pins can be used as DigitalOut pins. If not then the assumption fails, as does the entire test. Is this an acceptable solution?

[BlackstoneEngineering]

@maclobdell are the assumptions tests an acceptable solution?

[BlackstoneEngineering]

Marking as resolved.